Range computing apparatus for gnomonic maps



Oct; 8, V1957 E. NYY'ssoNEN RANGE: COMPUTING APPARATUS FOR GNoMoNIc MAPS Filed July 16, 1953 v 5 Sheets-Sheet l Filed July 16, 1953 Oct. S 1957 E NYYSSQNEN 2,808,649

RANGE COMPUTING APPARATUS FOR GNOMONIC MAPS JEL-LE By M /w frye/ky?.

Oct.. 8, R957 E. NYYssoNEN.

RANGE COMPUTING APPARATUS FOR GNOMONIC MA'PS Filed July 16, 1953 5 Sheets-Sheet 5 HND /7 rae/'VE f @et 8, w57 E. NYYssoNEN RANGE COMPUTING APPARATUS FOR GNOMONIC MAPS 5 Sheets-Sheet 4 Filed July 16, 1953 INVENTozL" E//vmeo /v TTOE/YEY l Qct. 8, 1957 E NYYssoNEN I 2,808,649

.RANGE COMPUTING APPARATUS FOR GNbMoNIc MAPS Filed July 16, 1953 5 Sheets-Sheet 5 INVENTOR. E//VHED fvmsoNf/v United States Patent ,0

RANGE CONIPUTING APPARATUS FR GNOMONIC MAPS Einard Nyyssonen, Watertown, Mass., assigner to the United States of America as represented by the Secretary of the Air Force Application July 16, 1953, Serial No. 368,459

This invention relates to mapping and charting apparatus generally, and more particularly to a plotting board and cooperating means for accurately determining range or great circle distance on a gnomonic map or chart between any two selected points or locations on the map.

In carrying out the invention, the actual bearings, latitudes and longitude, of the selected point or points to be located with respect to some other fixed point are furnished or are otherwise determined and the position located on the gnomonic map, the azimuth angle or bearing being set up in the apparatus as indicating the true azimuth angle between the great circle arc or reference line from the plotting station to the represented true north of the gnomonic map and a second great circle arc or reference line from the plotting station to the point or location to be determined on the gnomonic chart. This invention is not primarily concerned with the apparatus for determining this azimuth angle or bearing and reference is made thereto as briefly as possible.

The invention relates primarily to the means for determining actual distance between any two selected points on a gnomonic chart, one of these points being indicated as any selected relatively xed point or plotting central and the range being the distance therefrom to the other selected point.

Gnomonic charts are primarily use-d in plotting because only with this type of chart or map does the earths great circles appear as straight lines and its spherical angles as plane angles. However, any flat representation or" the spherical surface of the earch, such as a gnomonic map, is necessarily distorted and any angles, or distances, on the chart must be corrected for the distortion.Y

Gnomonic charts are drawn by projecting from a sphere, by means of radial lines from the center of the sphere to a plane tangent to the projecting sphere, a representation of the earths surface. The scale of the gnomonic chart or map is determined by the ratio of the diameter of the projecting (map) sphere or globe with respect to the diameter of the earth. With this type of projection, angles or bearings on a gnomonic map are equal to true angles or bearings only at the point of tangency. Range or great circle distances on the gnomonic chart, on the other hand, is never true distance or range.

Range from any fixed selected point on the gnomonic map, usually termed the plotting central, to any other selected point on the gnomonic map, usually termed herein as the scanning point, can be accurately determined by my improved apparatus. The location of the plotting central on the gnomonic map and its imaginary point on the projecting (map) sphere which represents the earch are radially aligned, also the imaginary point of tangency between the gnomonic map and sphere are radially aligned, with respect to the center of the sphere. The scanning point on the gnomonic map represents any other selected point to which the range from the plotting central is to be determined.` This scanning point is also aligned with a corresponding (scanning) point on the map projecting sphere and the center of the sphere. The range problem is solved by either computing the length of'this arc on the sphere, or by computing the angle subtended at the center of the imaginary projecting sphere and then converting to linear distance, since, in the nautical system, one minute or arc represents one nautical mile. This range angle is computed by my improved apparatus directly from the surface of a gnomonic map. The radial lines which connect the locations of the plotting central and the scanning point with the center of the projecting sphere are imaginary, and my improved apparatus reproduces these lines mechanically, also the angle is measured electrically and converted to range distance.

In carrying out the invention a plotting board is employed to support the selected gnomonic map, and my apparaus includes a pantograph device. The location of the scanning point on the gnomonic map on the plotting board is reproduced by means of the pantograph from bearing direction data and apparatus, and is represented by the center of a universal joint with one shaft thereof positioned with its axis extending through the center of the imaginary sphere, the location of the plotting central is reproduced by an adjustable and rotatable housing oriented so that its axis extends through the imaginary position of the plotting central and the center of the imaginary sphere 4and the angular relation between the respective axes is a function of the angular or, great circle distance from the plotting central on the gnomonic map to the scanning point.

Other objects and advantages of the invention will become apparent from the following description and accompanying drawings in which like reference characters refer to like parts in the several figures of the drawings.

Drawings Fig. 1 is a schematic perspective view, illustrating the general method and apparatus employed in my improved range plotting board.

Fig. 2 is an enlarged vertical sectional view taken through the computer assembly in zero adjustment, or adjusted for determining range or distance from the point of tangency ot the gnomonic map to the scanning point-with respect to its imaginary spherical map.

Fig. 3 is a side elevation of the range computer assembly shown in Fig. 2, but taken at right angles to Fig. 2, parts thereof being broken away and shown in section.

I Fig. 4 is a top plan view of the parts shown in Fig. 2.

Fig. 5 is a schematic perspective view illustrating the pantograph arrangement which is located below the surface of the gnomonic map support or table for determining the azimuth angles or bearing directions of points or locations, around any point on the gnomonic map, such as the plotting central.

Specification Referring to Fig. l of the drawings a gnomonic map is indicated schematically by the reference numeral A, and shown mounted on a suitable plane support, or map mounting board, or table 1. The imaginary map projection globe or sphere is indicated at 2, in dotted lines, having a conventional point of tangency to the plane of the gnomonic map surface at some point 3, usually however, at the center of the gnomonic map A.

The table 1 carries a pantograph supporting bracket 4 fixed thereto, upon which a pantograph 5 is mounted, pivoted at 6. The pantograph lcomprises the usual pivoted parallelogram frame comprising the long parallel bars or arms 7 and 8 and the scanning larm or bar 9 eX- tending above the top of the table 1, having a scanning point 10 at its free end, the parallel link or short arm 11,

forming the parallelogram frame, pivoted together at points 12, 13, 14 and 15, as shown in the drawing. The reproducing point of the pantograph 5 is indicated at 16; and while the reproduction may be of any'idesred proportions I preferably make the length of the scanning arm 9 between the lscanning point r1t) and pivotu 13 equal to six times the length of the arm portion 8a from the pivot l to thereproducing point 16. The length of'arm 11 between the pivots 12 and 15 and length on arm portion 9a between pivots'l and i4 is similar, or one'sixth the distance on arm 9 from pivot13 to scanning point lll.Y This provides Aa 6to l proportional movement between the scanning point 1d Iand the reproducing pint'16.

Also lixedly mounted on the table v1 rearwardly thereof is` my range computer assembly,shown indetail'and described in connection with Pigs; 2,13 and 4. rIts locationinliig.. l isvery schematically indicated'at 17 with its universallyy pivoted tilting center representing the center .ofa second or smaller imaginarysphere or vglobe vISshQvvn in dotted lines having, inthe present instance, ardiamreter one sixthlthat .of the larger gnomonic projection sphereA or globel2 from which the gnomonic map was made,Y also dotted.l The point of tangency 3 'and 'scanning -point are,.of, course, reproduced by the range cornputer `pantograph reproducing armat'3fz and 10a respectivelyrelativetoan imaginary smaller (gnomonic) chart Aa shown in dottedlines, one sixth the size of 'the physical gnomonic chart A on the table 1.

Since the fplotting central or point from which the plotting is made is usually at lsome definite ,location on the gnomonic map A, such `as any point 19, hardly ever at the-point of tangency 3, this point is also reproduced at 19a on the smaller imaginary gnomonic map Aa by the tiltingof the axis of the assembly, relative to the pointoi tangency 3a sothat its axis passes through center of imaginary small globe, i8. This point oftangency 3a may be alsoinitially located bythe pantograph reproducing arm scanning pointpl, as will be later explained, for initially setting the 'devicefor measuring any range such as indicated at 20, and the corresponding great circle distance-from the plotting central V19 tothe adjusted position of the 'scanning point ltlat the selected point or location on the gnomonic map and measuringralso the range angle rZtl with reference to the small imaginary sphere 18, 'representing distancefrorn 19a to 10ft on the smaller imaginary map Aa.l Referring todFig.` 1 the distorted gnomonic map range or distancebetween the plotting central 1'9 .and'any selected scanningpoint 10 is indicated at'22a, while fthe true range distanceon the surface ofthe"imaginarymap'sphereZ between similar points 19t andiltia is indicated by 2012 r y. I

The range computer @assembly supporting bracket is fixed on the map supporting table 1, as `previously indicated. This bracket is'in'dicated in Figs. 2, 3 and 4 by the reference numeral and is formed with an annular supporting ange 26h'avin'g a center at `27. An adjustable support or plate 28 of generally U shape rests on the llange 26, is rotatably adjustable about the center 27, and clamped in any adjusted position by the retainer plate 29 and screws 29a. The adjustment plate 28 is formed .with depending 'tr-unnion bearings 30 f having aligned axes passing through the center 27' below the plate 28 as shown.

The main housing 34 of Ythe range lcomputer assembly is tiltably hung on trunnions 3l journalled in the Vbearings 30, `and bearing caps* 32 provided may be` tightened 'by the cap screwsV 33 to retain the main or central housing 34 with'its axis 35 in any adjusted inclination, in one plane. Rotatory adjustmentof the supportingplate 28 provides means for adjusting theV inclination of thefcentral housing axis'35 in a second intersecting plane, the purpose of which will later appear.

`vAnnular bearings 36, fixed within the central housing 34 as shown in Fig.` 2, rotatably carry a bell-shaped potentiometer'support means or'housing' 37 having' spaced trunnion bearings therein with aligned axes disposed perpendicular to the vaxes 35 in a plane parallel to the rotative plane of the plate 28, intersecting the axes of the trunnion bearings 3! at the center 27. A tubular sector arm structure 38 is ixed by a set screw 39 on a short shaft 40 having its ends journalled in the trunnion bearings of the tubular rotatably adjustable bell-shaped housing 37. The bell-shaped housing 37'is' therefore free to rotate on the bearings V36,`and the sector arm structure 38 is free to tilt about the axis of the shaft 40. Therefore the sector arm 38 is adjustable to any angle less than about 90 in any plane passing through the axis 35 of the central housing 34, regardless of the'angular and rotative adjustment of the housing 34 on the trunnions 3l and supporting ange'26. The bell housing 37 is slotted at its front side as indicated at 37a, permitting the sector arm 3S to pass therethrough incident to its adjustment, an opening 37b being provided at its opposite side to accommodate-the curved actuating or geared segment arm 38a projecting from the sector member 38 and iixedto the member 38 by fastenings 41 for setting the potentiometer. A

A gear-tooth rack 42, Aformed on the curved arm 38a, meshes with a pinion gear V43 for adjusting the position of a slider of a potentiometer '44 xed in the side enlargement 45 of the bell shape housing 37 and having a lsubstantially -linear electrical output. A side plate 46 on the yarm 38a projects over the side of the slider adjusting pinion 43 retaining it in meshing rotation with the rack 4 2 and for controlling theactuation of a limit microswitch 48 to interrupt the electrical4 circuit to the electrical range angle indicator at `a predetermined angular movement of the arm 38a. Adjustment of the potentiometer slider tozero position relative to the meshing position of gear 43 can be accomplished by adjusting the potentiometerv bodyy relative to the potentiometer shaft and pinion, for which purpose elongated lslots are provided in the mountingilangeof theA potentiometer. The periphery of the thin side plate 46 has a cam portion for operating .the micro-switch@ to prevent an improper range indication when the sectorparm member 3S swings too far, for instance, to the left, as shown in Fig. 2, the cut away end 46a or cam portion permits actuationiof the micro switch control element. Y A

T he bell'fs'hape housing 37 is provided with -an adjustable stop or set ,screwl 49 `engageable with the sector arm 38 Vvat '56,* whereby the initial predetemined aligned or zero position ot `the sector arm axis 51 with the axis of 'housingf34 can beweasily determined.

The sector member or arm 38 is formed withV a cylindrical. guidebore 52 having 4its center on the axis 51 and a shaft 53 is slidablynjournalledlin the bore 52 having :a universal actuating connection inthe form of a universal jointftli'ereiri at`54, the; otherend`55 `of the shaft being fixed. in reproducing end Saof the pantolgraph arm 8 at 16 perpendicular to the gnomonic map surface.

A The electrical conductors orleadwires from the potentiometer`44 -arenot shown in'rFig. 2 but they are liexible andexten-d'upwardly'and into thevhollow bore 56 of 'spindle 60 and lare fastened tothe-respective slip 'rings 57,l 58 andi59 which are insulated` from Veach other and mounted on the upper end of the bell-shaped housing spindle 60, above the bearings 36.

4 An annular housing 61 .is lixed on,`andk above, the tiltable support 34 having inspectioniwindows 62, and -a .capV 63 is fitted thereon having an electrical conduit open- *l infgf64 to receive a flexible conduit 65 havinlg the leads or ,conduits 65a, etc. whichA extend to a suitable calibrated electrical device 65e for computing l the electrical output of the potentiometer inl terms of thejadjiisted angular relation`of the axis SI'Arelative tothe axis 35.v The ends ofthe leadsy 5aqexten'dingmwithin the capt?, are, of lcourses-*connected to suitably relatively insulated Aseparate brushes'v` in contact respectively with slip rings V57, 58 `1fdh59. i

The' plotting board and pantograph also includes a means for locating an unknown transmitter on the gnomonic map (such as a 'radio transmitter) from bearings furnished by at least two (or more) direction nder stations of a network the positions of which are located on the map. To initially locate the unknown transmitter on the |gnomonic map, with respect to lthe nder stations, from a desired pointed or the plotting central 19 aforesaid on the map, for the purpose of determining true distance or range from the plotting centra on the map to the unknown transmitter, as specifically set forth above, the means for initially locating the unknown station on the gnomonic map preferably comprises a pantograph extension or arms connected to the two arms 7 and S so as to move therewith and reproduce the position of the scanning point 10 below the map supporting surface of the table l. (See Fig. 5.)

Locator stations are `also initially located and fixed under the table with respect to the locations of these station locations on the :gnomonic map, directly under the said locations on the map A or on a smaller relative scale. Bearing, actuator rods extend outwardly from the reproduced locator stations (under the table) and are swingable -about the center or vertical axis of the locator stations, parallel to the map supporting surface of table 1. The outer end of the second scanning arm (below the table) is swivelly and slidably connected to the swingable arms below the table aforesaid so that when the scanning point 10 is shifted the `arms are either shifted about the simulated locator station pivots, or slide in the swivel connection. Swinging of each station locator arm correspondingly rotatably `adjusts a shaft which is connected to a potentiometer through la universal joint interposed between the ends of the shaft and the angular adjustment at opposite sides of the universal (in a plane parallel to the table top) `corresponds to the angle between the point of tangency on the gnomonic map land the position of the locator station on the map. Since this angle is a ran-ge angle from the point of tangency it can easily be determined. This is done by scribing an arc on the map from the position of the locator station to the meridian through the point of tangency. This angle is the difference in latitude between the point of tangency and the point of intersection of the arc and the said meridian.

It has been determined that the relation between the plane angle on a `gnomonic map and the spherical or true angle at any point on the earths surface correspond to the angular displacement of one shaft of a universal joint, away from the axis of the other shaft, when the angular relation aforesaid of the shafts is properly oriented so as to be equlal to the angular displacement from the point of tangency of the gnomonic map to the location of the said point. With this angular setting as aforesaid, when the station locator arms are swung by the lower pantograph reproducing arm, true :angles are generated by the output sh-aft of the universal joint 4and these are measured by .tmeans of the potentiometers. t

The potentiometers corresponding to the location stavtions, not shown, are provided with a dierential input -by means of which the dilerences or deviations between nthe correlated angles generated by the locator arms and '.the reported azimuth angles or bearings and `can be deztermined. These deviations are measured by means of the potentiometers and are then arranged in a suitable electric circuit. The above-mentioned selected point, the most probable location of the transmitter is determined by a scanning process involving these features of the plotting board.

rI'he azimuth or bearing with respect to true north of the selected point can be then determined by means of a computer somewhat similar to the locator stations but without -a ydifferent input to the potentiometer thereof.

The structure for determining the azimuth angle or bearing of the selected point is schematically illustrated in Fig. 5, the parts of the pantograph and plotting board `for determining `bearing that are illustrated .thereon `being referred to by reference characters.

The arms of links 7, 11, S-Sa and 9 are shown in-Fig. l, however the range computer assembly and connections are omitted from Fig. 5. The arms 7 and 8 are formed with rigid downwardly extending bracket extensions and 101 which extend below the map supporting table A at 100e land 101:1 in parallel relation to the arms 7 and 8, and a second reproducing pantograph arm 103 is connected thereto at points 104 and 105. In actual practice the lengths of the arms 100a, and 101a and 103 is one half that of arms 7, 8 and 9 so that the ratio of movement of the reproduced scanning point 106 to the upper scanning point 10 is 1:2. This reduction is for convenience like the lower ratio of movement of the reproduced scanning point 16 to that of the map scanning point 10. At the scanning point 106 of'lower pantograph arm 103 are two (or more) swivel guide bearings 107.

A housing is adjustably positioned under the table to locate a vertical shaft 108 under the table 1, with its axes located perpendicular to the map ysurface,^in a position corresponding with a previously located transmitter locator station 113 on the gnomonic map las explained above. Where the ratio of scanning point 106 is half that of scanning point 10 this would be in relation to an imaginary gnornic half size map (not shown). The lower end of shaft 108 carries gear means 109 which correspondingly adjusts a second shaft 110 having a universal joint 111 therein, the outer end portion 112 of the shaft 110 being mounted in suitable bearing means for adjustment of the angle of the axis of portion 112 from the axis 11011 (of shaft portion) carrying the bevel gear means 109. This angular adjustment is in a horizontal plane parallel to plane of the map (for convenience) and is made such that the angle between the point of tangency 3 and the selected transmitted locator station position 113 equals the angle between the axis 11011 of the shaft 110 and the axis of the shaft portion 112. An index pin 114 is provided in the adjustable supporting housing for the universal joint 111 in order to zero index the universal joint to provide the proper orientation of the correction produced by the universal joint (a clamp is provided on the lower gear means 109) a further clamp is provided on the potentiometer shaft for orienting the potentiometer 115 to corresepond to true north.

When the respective universal joint shaft connections are adjusted angularly, as indicated above, the scanning point 10 can then be moved on the gnomonic map surface to the said selected point and the output of the potentiometer 115 connected to meters which indicate the bearings of the selected point or transmitter station location. Range between the unknown station and the plotting central can then be accurately determined as before and is the subject matter of this invention.

Operation range` Assuming that some unknown range on the gnomonic may A is to be determined, from a known point or plotting central 19 to a second point for instance where the scanning point 10 of the pantograph scanning arm is positoned as in Fig. l. The scanning point 10 may be shifted to the plotting central location 19 and this movement displaces the reproducing end 8a of the pantograph arm 8, and the taxis 51 of the tubular sector arm 3S is displaced relative to the axis 35 of the housing 34, the range signal potentiometer 44 creates a voltage proportional to the angular displacement aforesaid of the shaft axis 51 from the axis 35 of the range computer assembly. To dispose the direction of the axis 35 in alignment with the plotting central 19a on the imaginary map Aa and the center of the imaginary sphere 18 as shown in Fig. l by the line 119, the securing means 29 and 32 (Fig. 2) for the main housing 34 is loosened slightly and the housing 34 is tilted, and turned if necessary, to dispose the axes 35 land 51 in alignment. This adjusts the range potentiometer 4 4 to zero output voltageat the position `of 'the' plotting" central. This "alignment'can accurately be determin`e`d`by :rotatingthe bell housing 37 'on its supporting bearings" SGjandadjusting' 'the 'housing `35 to' obtairx""ze`ro` 'range'eleictrical output "throughout said rotative adjustment about-the axisoff'plo'tting central position.

' After the Vmainhotising ofthe range'computer isV secured in its adiust'edposition the scarini'ngpoint V10 of the scanning armt9is movedv to the" selectedor indicated point ony the gnomonic map A representing the unknown transmittertandthis adjustsaheposition of the pantograph reproducing ipoint'16to a corresponding position 'on the'smallerimaginaryrnapAa,` theE shaft or rodY por ktiont55 secured' in thearmtaat 16, 'through universal54, shifting the tubular sector arm"38,' `'which shifts 'and inclines the"portion"53iof the "shaft' 55 `above the universal -54. *This establishesian imaginary range angle, 'such (as 20 between the 'plottingcentral andl the selected unknown range'point on'the gnomonicrmapi'AA and this range angle yis duplicated in the `range'computer Vat 20a, -the movement or'iinclination ofi-'the tubular-sector arm 38 shifts the raclctZr to correspondingly adjust the range potentiometer# toV provide :an electrical potential output from the potentiometer proportional to-theindicated or adjusted range angle, and the corrected electrically responsive indicator connected -to 'thepotentiometen and calibrated in-range\angles, and if'y desired, calibrated in nautical miles and will indicate the range angle or distance between a predetermined plotting central (located -at any point on theV gnomonic map A) and any other selected point on the gnomonicmap.

While the inventionlhas beendescribed in connection kwith one speciiicembodiment, somewhat schematically illustrated, the principles yinvolved as shown anddescribed are :susceptible of modification and slight changes. Therefore the invention is to be limitedY only as indicated by the scope of the appended claims.

I claim:

l. A range computing apparatus for computing range on a gnomonic may comprising a supporting means having a plane map supporting surface for mounting a gnomonic map thereon, a pantograph mounted on the supporting means @and having a scanning point movable 'over the supporting surface to any selected point on the gnomonic map mounted thereon, said pantograph having a reproducing end-movable proportional to movements of the scanning point over the gnomonic'map to trace an imaginary gnomonic map in la space proportional to the gnomonic map on the supporting surface, a range computer assembly supportxed relative to the pantograph supporting means and the map supporting surface,

an adjustable range computer housing adjustably fixed to the assembly support, and having a central axis, said housing being adjustable to dispose said central'axis at any predetermined angular relation to a line from the point of tangency of the gnomonic map to the center of the imaginary gnomonic map producing globe or sphere for the gnomonic map on the supporting surface, said computer housing including computer `means carried thereby comprising a first range computer assembly part rotatably mounted in the computer housing and rotated on an axis coincident with the computer housing axis, a second cooperating movable range computer part pivotally connected to the first range computer assembly part Ahaving an axis angularly tiltable relative to the axis of VtheV first range computer part in a plane coincident with the Yfirst range computer assembly part axis to conform vwith any line fromany selected point on the gnomonic may to the center of the said imaginary gnomonic map reproducing sphere orglobe, a' universal lactuating connection between the 'reproducing 'end on Vthe pantograph and the'second movable range computer part for tilting the same proportional to movement of thev scanning end over the gnomonicmap, and angle measuring means connected between the firstfrange Vcomputer lassembly part vland: second :rangelassem-bly part for measuring they angular i8 relation between'ithe -axes of said first range'computer assembly partand the second movable range computer part wherebyl therange 'angle 4between any' two` selective points'on the gnomonic lmap'can `be reproduced tbythe positionsof theiaxes of the said first; range computerassembly part and said second movable range computer part, andthe said reproduced range z ariglemeasured`v to indioate'the range angle between the corresponding points on the gnomonic map and converted -to nautical distance. 2.` A range computing apparatus for computing range on a gnomonic mapcomprising a supporting-means-having a plane map supporting surface formounting Ia gnomonic map thereon, a pantograph'mounted on the supporting means and having a scanning point movable 'over the supporting surface to any selected point'on the gnomonic map mounted thereon, said pantograph lhaving a reproducing point movable proportional `to movement of the scanningpoint over the-gnomonicmap to trace an imaginary gnomonic map in space proportional to the gnomonic map on the` supporting surface, a range computer assembly'sup'port fixed relative lto the pantograph supporting means and the map supporting surface, a range computer housing adjustably fixed to the assembly support having a central axis adjustableto'any predetermined angular relation to a linefrom the point off tangency of thegnomonic map to the center of the imaginary gnomonic` map producing globe or vsphere for the gnomonic map on the supportingv surface, said computer housing including computer meanscomprising a iirstpart rotatably mounted inthe computer housing on an axis conicident with the computer housing axis, asecond 'cooperating movable part pivotaily connected to the,` first part having an axis'angularly tiltable relative to the Vaxis of the first part in a plane coincident with the first part axis to' conform' with any line from any selected point on the gnomcnic map toV the center ofthe said imaginary gnomonic map reproducing sphere or globe, a univeral actuating connection between the reproducing point on the pantographand the second part for tilting the'same proportional to movement lof the scanning point over the gnomonic map, and angle measuring means connected between the first and second parts for measuring the 'angular relation between the axis of said first and second parts whereby the range angle between any two selective points on the gnomonic map can be reproduced in space by the relation of the axes of the said first and second parts,`and the said reproducedl range angle measured toindicate the range angle between the corresponding points on the gnomonic map and converted to nautical distance, in which said range angle measuring means includes potentiometer means carried by one of said yfirst and second parts having a substantially linear electrical output, and potentiometer setting means on the said other of said first and second parts for actuating the potentiometer` proportional to the angular displacement of the said axis of the second part relative to the axis ofthe said first part, and range angle indicating means connected to the electrical output of said potentiometer, for converting the electrical potential output of said potentiometer into degree of angular displacement of said axes to indicate the angular displacement of the said axesV of the said first and second parts to indicate the angular range distance on the gnomonic chart between any two selected points thereon. 3. In a range computer apparatusfor computing range angle distance on gnomonic maps, a plotting board having a map supporting surface for receiving a gnomonic may thereon, a pantograph mountedadjacent the map supporting surface having a scanning point movable over the map supporting surface to any selected or indicated points on a gnomonic map thereon, Asaid pantograph having a reproducing end correspondingly movable in spaced relation to the supporting surface to describe an imaginary gnomonic map proportional to the physical gnomonic map on the supporting surface, and rangecomputing means connected' to-'thereproducing end of the panto'graph for physically reproducing the angular relation between any two reproduced points on the gnomonic map and the center of an imaginary globe corresponding to the gnomonic map globe for the gnomonic map at point of tangency, and electrically operated means connected to said range computing means for measuring said reproduced angular relation, to indicate the range angle incident thereto.

4. A range computing device for gnomonic maps, cornprising a plane support for mounting a gnomonic map thereon, a pantograph device having a scanning point movable over the plane support to reach any point on a gnomonic map when mounted on the plane support, said pantograph having a reproducing arm with a reproducing end extending beyond the edge of the plane support and having a reproducing point to reproduce the movements of the scanning point over the gnomonic map at one side of the plane support, a computer support fixed at one side of the plane support adjacent the said pantograph reproducing end, a first range computer part having a central axis, and rotatable thereabout and universally tiltable on the computer support to dispose said axis in parallel relation to any line from an;l point on a gnomonic map on the plane support to the center of the imaginary map producing sphere for the said gnomonic map, a second range computer part pivoted on said first range computer part about an axis intersecting said first range computer part axis for swinging and rotative movement on said first range computer part axis and having a range angle determining axis inclinable by swinging and rotative adjustment of said second range computer part about its pivot and rotative on the first range computer part to dispose said range angle determining axis paarallel to any second line from any other point on the gnomonic map to the center of its map producing sphere, clamp means for securing the first range computer part on the computer support in its adjusted position, and positive actuating means connected between the reproducing end of the pantograph and the second range computer part for adjusting the range angle determining axis of the second range computer part about its pivot relative to the central axis of the first range computer part in accordance with the movement of the reproducing end of the pantograph, and range angle determining means connected between said first range computer part and second range computer part for determining-the relative angular relation between said central axis and said range angle determining axis of the first range computer part and second range computer part to measure the range angle between said central axis and said range angle determining axis thereof.

5. Apparatus as claimed in claim 4, in which the range angle determining means comprises a potentiometer having la linear electrical output, carried by either said first or said second range computer parts, and means carried by the other range computer part for adjusting the potentiometer proportional to the relative angular relation between the said central axis and said range angle determining axis said first and second range computer parts, and electrical range angle indicating means connected to the potentiometer for determining the angular relation between the central axis and said range angle determining axis of' the said first and second range computer parts and converting the same to range angle, as indicated between the said any two selected points Von the gnomonlc map.

6. Apparatus as claimed in claim 5 in which the first range computer part is journalled for free rotation on said central axis and the second range computer part is pivoted to the first computer part by means on an axis perpendicular to and passing through the first range computer part central axis to swing in a plane including the first range computer part central axis said second range computer part having a guide bore thereinV concentric to the said second range computer part axis, a pair of shafts universally connected together intermediate their ends, one shaft being guidingly received in said bore,

said other shaft being fixedly connected to the reproducing arm of said pantograph in concentric relation to said reproducing point and perpendicular to the direction of movement of the reproducing point as the scanning point is moved over the surface of the gnomonic map.

7. Apparatus as claimed in claim 6 in which the potentiometer is of the linear output type and is fixed on first range computer part, and includes a pinion gear for actuating its slider element 'and the second range computer part includes a gear rack segment fixed thereto in meshing relation with the pinion.

No references cited. 

